This invention relates to a method for welding copper or a copper base alloy and iron or an iron base alloy to obtain a weld metal which is free from cracks and less in segregation at the welded portion.
According to the prior art method for the welding of copper or a copper base alloy and iron or an iron base alloy, there has been such drawback that the welded portion tends to form cracks and is marked in segregation to become low in corrosion resistance. Further, the welding of copper and iron to form a weld metal having a welded portion free from cracks and high in corrosion resistance has come to be required, like in the welding of a copper-made conductive section and a steel-made high strength section as seen in, for example, U.S. Pat. No. 3,564,316 (Composite Commutator Bars). In the prior art attempts, there have been utilized such processes that nickel or a high nickel alloy known as Inconel is welded on an iron type base material and then the padding and a copper type base material are welded together by use of a welding rod of copper type base material, or nickel or the high nickel alloy is welded on a copper base material and then the padding and an iron type base material are welded together. Recently, there have been adopted such processes that a mild steel and copper are welded using butt beveling by electron beam welding, or Inconel 600, aluminum or a copper-nickel alloy known as Monel metal is incorporated into the weld metal, thereby preventing the formation of cracks at the welded portion by the electron beam welding. According to these processes, however, the growth of column-like crystals in the weld metal is so marked that cracks are liable to be formed at the welded portion. Further, the segregation of copper and iron in the weld metal is so great that the welded portion is low in corrosion resistance. These drawbacks become serious problems in the case of welding of, for example, the aforesaid commutator bars.